Many scholars have attempted to analyze prison argot in different countries in the world. Nevertheless, the features of this variety of language have been fragmentary treated. Furthermore, in the Kenyan context, the area of prison argot has received the total silence of scholars in the linguistic field. The main aim of this study is to analyze the features of the Kenyan prison argot which is generally referred to as Kiswahili ya jela. Kiswahili ya jela is an ungrammatical Swahili phrase which in standard usage should mean the Swahili language of prisons. However, in the prison context, Kiswahili ya jela means a language full of tricks or lies. Thirty prisoners were randomly selected from Kibos and Kisumu Maximum Prisons to participate in the study. The contextual-dynamic method was used to collect data from the respondents. This method mainly involves the use of observation and dialogue. Because of its qualitative nature, the data is subjected to content analysis. From this work, the following features are evident; borrowing of terms from other languages, reversing of syllables, coining of new prison-contextual lexemes and the formation of argot terms through affixation. This study also reveals that the Kenyan prison argot exhibits code-mixing and the use of ungrammatical structures. Synonymy and polysemy as semantic features are also revealed. This paper thus concludes that the Kenyan prison argot is a highly creative slang.